1. Field of the Invention
This invention relates generally to an apparatus for detecting temperature variations over selected regions of a living tissue, and to a method of detecting said temperature variations. The technique utilizes an encapsulated liquid crystal film that conforms to the contour of the tissue by evacuating air from between said film and said tissue. The crystals are responsive to changes in temperature of said tissue to display a color pattern on said film representative of said temperature variations.
2. Description of the Prior Art
Thermography, in its broadest sense, is a technique for detecting and measuring variations in the heat emitted by various regions of the body and transforming them into visible signals that can be recorded photographically. The technique is lately experiencing increased interest as a potentially significant aid in diagnosing abnormal or diseased underlying conditions, particularly those involving cancer of the breast.
At present, progress in the treatment of cancer of the female breast lies mainly in the area of early detection, with the diagnosis made and treatment instituted at an early stage of the disease. Although frequent physical examinations are recommended by the medical community, it is recognized that malignant tumors detected by this technique are often of such size as to indicate that the malignancy has already spread to other areas of the body. In order to provide earlier detection of the disease, much emphasis has also been placed on radiographic mammography. However, since this technique involves X-ray examinations, there is the danger of exposing the patient to excessive radiation. Mammography further requires the use of sophisticated equipment that is extremely costly, and the assistance of technically skilled personnel.
In recent years, significant scientific progress has been made in the use of thermography as an added instrument of diagnosis. All methods of thermographic examination are based on the fact that malignant neoplasms are surrounded by an extraordinarily large number of blood vessels. This serves to explain localized rises in temperature, stemming from the increased blood flow and metabolic activity, which are transmitted to the overlying skin surface. All work using thermography has been directed toward diagnosis by means of the differences in temperature of points or areas on the skin. For example, the skin temperature of the breast on the side with a tumor is found to be more than 1.degree. C. higher than that on the healthy side. Advanced carcinomas were warmer still, and it is possible to deduce the severity of the condition from the raised temperature.
Initial work with this technique was in the area of electronic infra-red thermography (EIT). This is a method of remote sensing of the infra-red radiation emitted by the surface of the breast. The scientific community was not entirely satisfied with this technique because of its limited reliability and the difficulty of interpreting the results. In this regard, the early equipment did not provide reliably informative thermograms in recording the small temperature differential between the tumor side and the healthy side of the breast. Furthermore, the slight temperature variations might well be caused by other conditions unrelated to the tumor. For example, the effects of the menstrual cycle, of hormonal contraceptives and of pregnancy have been found to cause minor day-to-day temperature changes which must be taken into consideration when reading the thermogram. Thus, it became accepted practice in the medical community that EIT, on its own, gave too many false-positive diagnoses, and that only a concurrent mammographic examination would allow greater certainty in diagnosing the condition as benign or malignant. The equipment required in practicing EIT was also extremely costly and often required the assistance of skilled personnel.
Continued research brought forth the development of liquid crystal thermography to obtain a multi-colored recording of the body region under examination. The liquid crystalline state is a particular form of matter lying midway between the solid crystal and a normal (iostropic) liquid. The use of liquid crystals in thermography evolved when it was determined that certain cholesterine esters with the properties of liquid crystals had the ability to react to variations in temperature by changing color. It soon became apparent that such cholesteric liquid crystals (CLC) might be used in science and technology as a temperature indicator.
The initial procedures practiced in the use of liquid crystals were extremely complicated and burdensome for the patient. In view of the fact that the temperature indicators had to be on a black background in order to show their color reaction with sufficient clarity, the patient's skin first had to be painted with a black undercoat, onto which the liquid crystals were then applied with a brush. The color reactions that ensued were visible only by daylight and were recorded by a camera on color film. Apart from the impracticality of this procedure for mass screening or routine examinations, it also has the disadvantage that the liquid crystals can be used only once. An additional problem with this technique is that it does not reproduce accurately the local vascular features. Moreover, the brushing technique is time-consuming and uncomfortable for the patient. Furthermore, heat diffusion causes unsharpness of detail in the images obtained thereby preventing a reliable diagnostic interpretation.
The technology further evolved to the point where the liquid crystals are now encapsulated in plates. The encapsulated liquid crystals (ELC), which form the basis of plate thermography, offers the advantage of changing the liquids into pseudo-solids, and improves the handling and processing of the liquid crystals. The plate registers temperature differences by means of the color reactions produced by the encapsulated cholesterine-type fluid crystals. As temperature rises, the reactions run through the color scale from red to green to blue, and the individual shades are able to indicate temperature differences of 1/10th of a degree centigrade. The color reactions take place a few seconds after the plate has been placed against the subject to be examined. The reaction is also reversible with equal rapidity in that the colors disappear quickly when the plate is removed from the subject to be examined.
Although the plate records zones of differing temperature with a relatively sharp outline, the use of plate thermography is still pretty well confined to clinical research facilities and/or use thereof in the doctor's office. The equipment is not suitable for use directly by the patient in her home, and is not sufficiently portable for use outside of the doctor's office.
Furthermore, because the plate is fairly rigid, it is not possible to shape it to the contour of the breast being examined. Thus, in examining the female breast, it is normal to diagrammatically divide the breast into four quadrants and then apply the plate separately to each one of the quadrants. A lateral view can also be obtained by having the patient turn sideways and applying the plate while the arm is raised. Color photographs can be taken of the color pattern produced on the plate. It will be readily appreciated that, due to the curvature of the breast, it is not possible to examine the breast with the use of only one plate. In this regard, it is important not to materially deform the tissue which is in contact with the plate since this would serve to distort the thermogram and thereby prevent a reliable diagnostic interpretation.
It thus became apparent that greater utility in the field of liquid crystal thermography would be possible if the plates were rendered flexible. The technology soon evolved to the use of such flexible plates in the form of thin plastic sheets superimposed on each other to form a composite film having the liquid crystals encapsulated therebetween. The construction may be deemed as representing micro-encapsulated liquid crystals sandwiched between two polyester sheets or substrates. The film is capable of being manufactured so as to be responsive to selective temperatures within a particular range of temperatures. This is a function of the crystals selected for use in the film. In other words, the crystals are selected so that they are operative in a temperature range that encompasses foreseen variations of body temperature in the region of the body under examination. The method of manufacturing such films is readily disclosed in the prior art as evidenced by U.S. Pat. Nos. 3,619,254 and 3,969,264.
Today, thermography using liquid crystals is receiving additional interest in diagnosing changes in venous and arterial blood vessels, bone and thyroid gland diseases, dermatological examinations, and in other clincial and physiological investigations.
In some applications, the initial thermographic test is then followed by another with the skin pre-cooled with cool air from a hand blower. The objective in this technique is to exclude the pronounced degree of heat formation and vascular visualization from physiological causes that is an almost regular feature of the sexually mature woman and of one receiving hormone medication. The thermographic images that result from this could well mask a pathological vascular picture. However, the areas of heat or vascular features stemming from pathological causes will reappear more rapidly than normal vascularization after cooling of the breast, or else will not disappear in the first place.
The use of liquid crystal thermography as an aid in detecting changes in the temperature of the skin, and particularly in detecting breast cancer, is noted in U.S. Pat. Nos. 3,830,224 and 3,847,139. In each of these patents, the liquid crystals are incorporated into the body of a garment, such as a brassiere, which is intended to conform essentially to the contour of the breasts. While the devices respectively disclosed in these patents produce a meaningful thermogram over certain regions of the breast, they have not proven satisfactory as an aid in diagnosing the condition of the entire breast. In this regard, it is important that the crystals be in contact with the entire region to be examined. The disclosed brassieres do not satisfy this requirement. In some instances, depending on the size and shape of the woman's breasts, some of the portions of the brassiere do not come in contact with the breasts at all while other portions contact the breasts to such an extent as to deform the breasts thereby producing a distorted thermogram. Furthermore, the brassieres have the tendency to hide or mark the sides of the breasts to prevent a reliable diagnostic examination. The present invention eliminates the objections and disadvantages present in using the aforesaid brassiere garments by providing an improved apparatus, and method of using the same, which causes the film to effectively conform to the contour of the entire breast without materially deforming said breast.